Snap-action electrical switch with slotted normally unstressed movable contact blade



March 9, 1965 v. R. ABELE ETAL 7 SNAP-ACTION ELECTRICAL SWITCH WITH SLOTTED NORMALLY UNSTRESSED MOVABLE CONTACT BLADE Filed June 27, 1962 jujwuforzs- %7/w02; a ez 8y l ma I 5 6;? a L United States Patent 3,172,970 SNAP-ACTION ELECTREQAL SWITCH WITH SLOTTED NORMALLY UNSTRESSED MOV- ABLE CONTACT BLADE Vernon R. Abele, Waukegan, and Donald R. Sterba,

Clarendon Hills, Ill., assignors to Fansteel Metallurgical Corporation, a corporation of New York Filed June 27, 1962, Ser. No. 205,743 3 Claims. (til. 200-67) This invention relates to electrical switches and, more particularly, to electrical snap switches having rapid operating contact members for opening and closing contact elements.

Snap switches, as heretofore known, generally utilized a contact spring which was internally stressed to set up a deformation. The prestressing provided an area of high sensitivity which, when acted against by an actuating force, caused the spring to snap over. With proper mounting of the spring upon a base, this snap, or rapid movement, was utilized to transport a contact element aflixed to one portion of the spring. With a second contact or, if preferred, a number of contacts, spaced from the movable contact element and in operative relationship therewith, a single pole or multi-pole snap switch was produced.

In manufacturing such snap switches, it was either necessary to preform the switch blank so as to set up a prestress condition therein, or else to manipulate a fiat spring into a specially designed casing to set up the prestress condition. Such handling was costly and, in addition, did not produce switches having consistent response at uniform levels of actuating force. This necessitated individual testing of each switch so that its actuating force response level could be determined. However, even with such individual testing, predictability and uniformity of actuating force throughout the life of the switch was not possible because the internal stress set up in the spring eventually produced material fatigue, which varied the response level.

The switch of the present invention is not subject to these difiiculties. It employs a contact spring which is preformed to a particular configuration rather than prestressed and is substantially free of internal stress when in normal condition. Internal stress is set up only during the momentary period of operation of the switch. And the unique structure of the contact spring permits its manufacture by a method wherein the response level can be accurately predetermined without the need for individual testing.

An illustrative snap switch embodying this invention consists of a base formed of insulating material, such as a thermosetting resin. The elongated contact spring of this invention is afiixed at one end to the base and it extends over the length thereof in cantilever fashion. The free end of the spring carries the movable contact thereon. At least one opposing contact is spaced from the movable contact so that make and break circuit operations are effected as the spring is actuated.

The contact spring has a longitudinal slot, preferably of elongated teardrop shape encircled by an inverted bubble or depressed portion about said slot. Both the slot and the depressed portion are formed in the spring during its manufacture by a simple stamping operation. Control of the bubble shape and size provides control of the actuating force necessary to operate the spring substantially independently of stresses that may exist therein, if any. This provides uniform operating parameters while permitting assembly-line manufacture of switches with substantially the same selected actuating force requirements.

The spring is mounted on the base with the wide portion of the teardrop-shaped slot adjacent to the mounting means. An anvil with an arcuate surface and a locating projection is afiixed to the base and extends partly into the elongated slot. At the opposite side of the spring from the anvil is an actuator which contacts the spring at its outer edges adjacent to the bubble or the preformed, depressed area.

Movement of the actuator causes the movable contact section or free end of the spring to snap downwardly from its normal upward pointing position. At the same time, the outer edges of the spring are forced downwardly while the anvil supports the inner edges of the slot in the spring. Thus, the inverted bubble, or depressed portion, is momentarily partially dished upwardly until the actuating force on the actuator is released.

In the preferred embodiment, two separate contacts are spaced about the movable contact section or free end of the spring. In unactuated condition, the movable contact is disposed upwardly and in contact with an upper or outer contact. In actuated condition, the movable contact is disposed downwardly and in contact with a lower or inner contact.

The invention is more fully described by reference to the accompanying drawings, in which there is shown an illustrative embodiment of the invention, in which each and every detail shown is incorporated hereby as a part of this specification, in which like reference numerals refer to like parts, and in which:

FIGURE 1 is a perspective view, partly broken away, of the snap switch of this invention;

FIG. 2 is a top plan View of the snap switch with the cover removed;

FIG. 3 is a perspective View of the spring element; and

FIG. 4 is an elevational view of the actuator.

The snap switch of this invention as shown in the drawings consists of a base 10 formed of an insulating material, such as a thermosetting resin. Embedded within the base are lead pins 11, 12 and 13. At their outer ends, the pins are formed as external terminals 14, 15 and 16, respectively. These external terminals may be formed to permit solder, or screw cap, or clip afiixation to the wires of the circuit in which the switch is to be utilized.

Lead pin 11 is secured to an elongated movable contact spring 20 by mushrooming its inner end 17 over an aperture 21 in the spring, or by welding or brazing or soldering as desired.

Lead pin 12 is aifixed at its inner end to an outwardly extending plate which acts as a lower or inner fixed contact 23. The plate is contained within a channel 24 on the upper surface of the base 10.

Lead pin 13 is afiixed at its inner end to an inwardly extending plate which acts as an upper or outer fixed contact 25.

The lower and upper fixed contacts 23 and 25, respectively, span a movable contact element 26 affixed to the elongated, movable contact spring 20 for engagement therewith, and are substantially aligned with each other.

Spring 20 is formed of sheet metal, such as beryllium copper or Phosphor bronze. An elongated slot 27, preferably of a teardrop shape, and a downwardly inclined rim 28 about the slot is formed in the spring, such as by punching operation or the like.

In punching the spring and forming a raised rim about the slot, the spring assumes a longitudinal arc configuration, such as seen in FIGURE 3.

After the spring has been formed, it is mounted upon base 10 in a cantilever position longitudinally disposed over the base by securing the inner end of lead pin 11 to the spring at an area indicated at 21.

An anvil 30 at the top surface of the base has a center protuberance 31 which extends into the slot 27 of the movable contact spring. The shoulders between the protuberance and the outer rim of the anvil bear against the inner edges of the slot.

An actuator with a lower saddle or U-shaped surface, transversely disposed with respect to the elongated contact spring, contacts the edges of the spring adjacent to the anvil 30. The actuator 34 has a knob 35 which protrudes through switch cap or cover member 36 which is secured to the base and encloses the switch elements.

If desired, gasket or other sealant material may be disposed between cap member 36 and base 10 to effect a waterand vapor-tight seal between the cap and the base.

The base contains two transverse extending orifices 39 and 40, which may be utilized to mount the switch to an external support.

In use, the actuating force on knob 35 is transmitted through the laterally arranged fingers 41 on the actuator body to the movable contact spring 20. Prior to actuation, the spring is disposed in a downwardly dished, upwardly pointing, unstressed position. When the external force is exerted on the spring through the actuator, the fingers on the actuator force the outer edges of the spring downwardly while the anvil 30 forces the inner edges of the slot upwardly. This causes the free end of the contact or spring arm to snap downwardly. The movable contact element 26, fixed to the free end of the spring 20, thereby snaps from contact with the upper, outer contact 25 into engagement with the lower, inner contact 23. The circuit between leads 13 and 11 is thereby opened and the circuit between elements 12 and 1. 1 is thereby closed.

While a detailed description of this invention has been provided, it should be understood that modifications may be made without departing from the spirit and scope of this invention.

We claim:

1. A snap switch comprising a base, an elongated, normally unstressed spring cantilever mounted on said base with its free end forming a movable contact, said normally unstressed spring having an elongated slot therein with a positive depression about said slot, a fixed contact mounted on said base adjacent to said movable contact, an upstanding protuberance on said base in engagement with the edges of said slot, an actuator engageable with said spring for transmitting switch actuating force to said spring adjacent to and laterally outwardly of the engagement of said protuberance with said spring to effect a rapid snap action of said spring from one position to an oppo- U site position whereby the movable contact selectively engages with and disengages from said fixed contact, and a cover member secured to said base.

2. A snap switch comprising a base, an elongated, normally unstressed spring cantilever mounted on said base with its free end formirn a movable contact, said normally unstressed spring having an elongated slot therein with a positive depression about said slot, a pair of fixed contacts mounted on said base adjacent to said movable contact with one fixed contact on one side of the movable contact and the other on the other side of the movable contact, a lead pin extending through said base and in engagement with said spring, an additional pair of lead pins extending through said base and respectively connected to said fixed contacts, an upstanding protuberance on said base in engagement with the edges of said slot, an actuator engageabie with said spring for transmitting switch actuating force to said spring adjacent to and laterally outwardly of engagement of said protuberance with said spring to effect a rapid snap action of said spring from one position in engagement with said one fixed contact to a position in engagement with said other fixed contact whereby the movable contact selectively engages the fixed contacts respectively, and a cover member secured to said base.

3. A snap switch comprising a base, an elongated, normally unstressed spring cantilever mounted on said base with its free end forming a movable contact, said normally unstressed spring having an elongated slot therein with a positive depression about said slot, said slot having a teardrop configuration with a wide end and a narrow end, the narrow end of the slot being disposed toward the movable contact, said depression having a configuration conforming to the configuration of said slot and extending substantially uniformly thereabout, an upstanding protuberance on said base in engagement with the edges of said slot, a fixed contact, an actuator having a U-shaped spring engaging portion engageable with said spring for transmitting switch actuating force to said spring adjacent to and laterally outwardly of engagement of said protuberance with said spring to effect a rapid snap action of said spring from one position to an opposite position whereby the movable contact selectively engages with and disengages from said fixed contact.

References Cited by the Examiner UNITED STATES PATENTS 2,627,754 2/53 Millard 200-67 2,860,208 11/58 Epstein 200-413 3,056,866 10/62 Karleen 20067 FOREIGN PATENTS 1,142,435 4/57 France.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. A SNAP SWITCH COMPRISING A BASE, AN ELONGATED, NORMALLY UNSTRESSED SPRING CANTILEVER MOUNTED ON SAID BASE WITH ITS FREE END FORMING A MOVABLE CONTACT, SAID NORMALLY UNSTRESSED SPRING HAVING AN ELONGATED SLOT THEREIN WITH A POSITIVE DEPRESSION ABOUT SAID SLOT, A FIXED CONTACT MOUNTED ON SAID BASE ADJACENT TO SAID MOVABLE CONTACT, AN UPSTANDING PROTUBERANCE ON SAID BASE IN ENGAGEMENT WITH THE EDGES OF SAID SLOT, AN ACTUATOR ENGAGEABLE WITH SAID SPRING FOR TRANSMITTING SWITCH ACTUATING FORCE TO SAID SPRING ADJACENT TO AND LATERALLY OUTWARDLY OF THE ENGAGEMENT OF SAID PROTUBERANCE WITH SAID SPRING TO EFFECT A RAPID SNAP ACTION OF SAID SPRING FROM ONE POSITION TO AN OPPOSITE POSITION WHEREBY THE MOVABLE CONTACT SELECTIVELY ENGAGES WITH AND DISENGAGES FROM SAID FIXED CONTACT, AND A COVER MEMBER SECURED TO SAID BASE. 